Abstract
PURPOSE: This work proposes a method for the simultaneous estimation of the exchange-dependent relaxation rate Rex and the longitudinal relaxation time T1 from a single acquisition. METHODS: A novel acquisition scheme was developed that combines CEST saturation with an inversion pulse and a Look-Locker readout to capture the magnetization evolution starting from the inverse transient Z-spectrum. The corresponding signal model, derived from the Bloch-McConnell equations, describes both the transient Z-spectrum and the Look-Locker dynamics. A model-based reconstruction approach is employed to jointly estimate Rex and T1 . The proposed method was validated using a numerical phantom and benchmarked against conventional CEST and Look-Locker T1 mapping in a phantom and in vivo on a clinical 3T scanner. RESULTS: The joint estimation approach demonstrated strong agreement with ground truth and conventional methods across a wide range of T1 and CEST parameters. The acquisition time was reduced by 20%-30% compared to standard CEST protocols, while providing a higher signal-to-noise ratio (SNR) in parameter maps. CONCLUSION: The proposed technique enables robust and efficient simultaneous quantification of CEST Rex and T1 in a single acquisition. It improves parameter map quality and reduces scan time, making it suitable for both phantom and in vivo imaging across a wide range of physiological conditions.